Delta H values for the 1:1 interaction of some sulfur-containing podands with Ag+, K+, Cu2+, Cd2+ and Pb2+ have been measured by calorimetry in methanol, For the Ag+ complexation, log K values were determined by potentiometry using an Ag+-ISE and, in this case, T Delta S could be obtained. The complexations were enthalpy driven and Ag+ exhibited remarkably higher complexation selectivity due to the increase of covalent binding between soft acid and soft base. The reaction enthalpy and entropy are discussed in terms of donor atom, end group and donor site effects, respectively. In the membrane transport study, efficient and highly selective Ag+ transfer was observed both in single and competitive cation experiments.